The cooling lubricants used during the material-removing machining of workpieces represent a considerable financial factor of the entire operating costs of such machines. The cooling and lubricating liquids used for grinding, milling, turning, boring, for example, are contaminated by the chips and other particles produced during machining. The mixture of cooling lubricant liquid and solids, in particular, chips, produced in the machine tool has to be treated in separate processes outside the machine tool so that the cooling lubricant liquid may be reused and the separated chips utilized. In addition to the separation of relatively coarse and voluminous chips from the liquid medium, the finer-grained particles and dusts, which usually are particularly abrasive, must also be separated from the liquid so that the liquid thus purified may be reused as a cooling lubricant in the respective machine tool. Several prior art devices are presented below as examples of efforts along these lines.
German patent publication, DE-A-199 47 724, discloses a device for purifying liquids such as, for example, cooling lubricants (KSS) of material-removing machine tools wherein the contaminated liquid is subjected to filtration. In a container for receiving the untreated liquid/chips mixture, a scraper conveyor is installed near the bottom thereof, the lower run of which transports the chips deposited in the lower container part in a slantingly upward manner to an ejection end. A filter drum vertically fixedly disposed in the liquid container serves as a filter unit that is inserted in a standing or pending manner from above in the main part of the liquid container and fixed so as to be non-rotating. A wedge wire screen is disposed as a filter means on the outer circumference of the vertically aligned filter drum and a plurality of purifying elements positioned in an angularly offset manner are provided for the purification of the wedge wire screen. Each purifying element consists of a scraper and a brush strip abutting the circumference of the filter drum when the purification device is rotated by a drive. This known treatment device is technically complex and requires considerable space.
U.S. Pat. No. 4,751,006 discloses a unit for treating and cooling a cooling lubricant which has been heated during the operation of the machine tool. The tool comprises a scraper conveyor having transversely aligned scraper strips for conveying off the chips in a storage compartment for the liquid contaminated by solids or chips. In the upper part of the storage compartment, a filter unit is provided that contains a continually driven traveling screen and a non-intermittent paper band filter resting on the same. The paper band of the filter is drawn off a roll, runs through the filtering station on the traveling screen and is rolled on a second roll together with the deposited solids.
Furthermore, European patent EP-B-1,474,268, for example, discloses a device for separating chips and cooling lubricant liquid from the material-removing machining of workpieces which has a storage container for the mixture of cooling lubricant liquid and chips and an endless conveyor disposed in the container. The endless conveyor is in the form of a scraper conveyor that runs over several deflection pulleys in the storage container and conveys the collected solids (chips) to an upper ejector via an oblique discharge portion. In the transition between the horizontal and the oblique portions of the scraper conveyor, a horizontally aligned filter drum is rotatably supported that is driven by the circulating scraper conveyor. A negative pressure is maintained in the filter drum so that the liquid is sucked inside the drum through the filter. The supportive assembly of the filter drum consists of a respective frontal internal and external supporting ring and axis-parallel spring elements and sealing means. The drum is provided with filter clothing on the outer circumference thereof. In this known device, the efforts required for effectively purifying the filter drum and its ancillary units in particular are a disadvantage. Furthermore, special measures are required for adapting the device to different or changing operating parameters of the respectively associated machine tool.